A conventional pulse tube refrigerator (Japanese Patent Application Laid-Open (kokai) No. 8-271071) is constructed as shown in FIG. 14. A high-pressure port 108a of a pressure vibration source 101 is connected to a main changeover valve 111, and a port 111h of the main changeover valve 111 communicates with a cold reservoir 103, a heat absorber 104, and a pulse tube 105 via a heat radiating unit passage 112. A hot end 105c of the pulse tube 105 is connected, through flow-rate adjustment means 122, to a first heat transfer tube 116 having a tubular shape and a port 106p of a phase adjustment changeover valve 106. The phase adjustment changeover valve 106 is connected to the high-pressure port 108a and a low-pressure port 108b of the pressure vibration source 101.
In the above conventional pulse tube refrigerator, when refrigerant flows from the phase adjustment changeover valve 106 into the hot end 105c of the pulse tube 105 via the flow-rate adjustment means 122, the refrigerant undergoes adiabatic compression, whereby the gas temperature within the pulse tube increases, and the wall temperature of the pulse tube 105 elevates to about 120° C. in a range extending from the hot end 105c of the pulse tube 105 to a longitudinally central portion of the pulse tube. Accordingly, the above conventional pulse tube refrigerator has a problem in that heat of the hot gas within the pulse tube 105 and heat of the wall of the pulse tube 105 are conducted to a cold end of the pulse tube 105, to thereby lower refrigeration capacity.
Moreover, since a heat radiating unit 102 of a heat exchange unit A is interposed between the main changeover valve 111 and the cold reservoir 103, the above conventional pulse tube refrigerator has a problem in that the free gas space increases, thereby decreasing the refrigeration capacity of the refrigerator.